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DRV8873: current sampling issue

Cherry Zhou
Mastermind 22235 points
Part Number: DRV8873

Hi Team,

The customer use the DRV8873HPWPR to control a DC brushed motor.

It's controlled in PWM mode with the following configuration:

MODE = 1, nSLEEP = 1, DISABLE = 0.

The current sampling points IPROPI1 and IPROPI2 are sampled separately during motor's forward and reverse. The voltage waveforms captured by the oscilloscope at IPROPI1 and IPROPI2 are as follows:

The waveform above with decreasing amplitude is PWM with a frequency of 20 KHz (the PWM driving the chip input is also 20 KHz).

And the peripheral circuit is as follows: 

Could you please help look into this case? Thanks.

Best Regards,

Cherry

  • 0
    TI__Mastermind 23431 points

    Hey Cherry,

    Can you please clarify what the observed issue is here?  

    At 390Ω sense resistors on IPROPI you are losing out on some accuracy - Io = (1100 * 5V)/(390Ω) = 14.1A (IO is the maximum drive current to be monitored).  This part has a 10A max.  Texas Instruments recommends the load current not exceed 8 A during normal operation. If slew rate setting of 2.6 V/µs (SR = 111b) is used when the load current is about 8 A, choose TOFF to be either 40 µs or 60 µs.

    Can you confirm your TOFF value?

    Best,

    Jacob